TO THE MEMORY OF THE LATE 



ALEXANDER AGASSIZ, 



TO WHOM THE SOCIETY MADE ITS FIRST AWARD 



OF THE WALKER GRAND PRIZE 



IN RECOGNITION OF HIS 'REVISION OF THE ECHINI. 1 

 AND OF 



ALPHEUS HYATT, 



LATE CURATOR OF THE SOCIETY. 



MY BELOVED MASTER AND FRIEND. WHOSE 



PRINCIPLES OF RESEARCH ARE THE 



KEYNOTE OF THIS MEMOIR. 



